Evaluation of traps and lures for mosquito vectors and xenomonitoring of Wuchereria bancrofti infection in a high prevalence Samoan Village

BackgroundElimination of lymphatic filariasis (LF) in Samoa continues to be challenging despite multiple annual mass drug campaigns aimed at stopping transmission by reducing the prevalence and density of microfilaraemia. The persistence of transmission may be partly related to the highly efficient Aedes vectors. The assessment of pathogen transmission by mosquito vectors and of vector control relies on the ability to capture mosquitoes efficiently. The aims of this study are to compare trapping methods to capture LF-infected mosquitoes and determine the role in transmission of the species of Aedes mosquitoes in the area.MethodsFasitoo-Tai village was the chosen site because of persistent transmission despite annual mass drug administration. Sampling methods included BioGents Sentinel (BGS) trap, human-baited collections (HBC) and the Centers for Disease Control (CDC) trap. BGS and CDC traps were baited with BG-lure, CO2, and/or octenol. Individual trap locations were geo-located and efficiency of sampling methods was evaluated using a randomized Latin-square design in two locations. Number of mosquitoes collected (male and female), as well as species for each trapping method were determined. Additionally, Ae. polynesiensis and Ae. (Finlaya) spp. females were pooled by trap method and analysed for filarial DNA. Infection prevalence was estimated using the PoolScreen software.ResultsThe BGS trap with any type of bait collected more mosquitoes compared to both the CDC trap and the HBC. The BGS trap baited with BG-lure collected more mosquitoes than with CO2 and octenol. There were no significant differences between trapping methods in terms of proportions of infected females collected. The prevalence of filarial infection in Ae. polynesiensis and Ae. (Finlaya) spp. was estimated at 4.7 % and 0.67 % respectively.ConclusionsThis study supports the use of the BGS trap for research on and surveillance of the mosquito vectors of LF in Samoa. The BGS trap is a suitable and safer alternative to HBC for sampling Ae. polynesiensis and Ae. (Finlaya) spp., which continue to be the predominant vectors of LF. Of concern was the high prevalence of LF in mosquitoes despite a recent mass drug administration programme. This highlights the urgency for updated policies concerning filariasis elimination in Samoa.

[1]  P. Lammie,et al.  Epidemiological assessment of continuing transmission of lymphatic filariasis in Samoa , 2011, Annals of tropical medicine and parasitology.

[2]  N. L. Nguyen,et al.  The impact of 34 years of massive DEC chemotherapy on Wuchereria bancrofti infection and transmission: the Maupiti cohort , 2001, Tropical medicine & international health : TM & IH.

[3]  D. Mabey,et al.  Neglected tropical diseases. , 2010, British Medical Bulletin.

[4]  R. Rao,et al.  Persistence of Brugia malayi DNA in vector and non-vector mosquitoes: implications for xenomonitoring and transmission monitoring of lymphatic filariasis. , 2007, The American journal of tropical medicine and hygiene.

[5]  H. Bossin,et al.  Comparison of the Centers for Disease Control and Prevention-Backpack and Insectazooka Aspirators for Sampling Aedes polynesiensis in French Polynesia , 2014, Journal of the American Mosquito Control Association.

[6]  S. Ritchie,et al.  Field Evaluation of Selected Traps and Lures for Monitoring the Filarial and Arbovirus Vector, Aedes polynesiensis (Diptera: Culicidae), in French Polynesia , 2013, Journal of medical entomology.

[7]  J. N. Belkin,et al.  Vectors of Sub-periodic Bancroftian Filariasis in the Samoa–Tonga Area , 1964, Nature.

[8]  J. N. Belkin.  The Mosquitoes of the South Pacific (Diptera, Culicidae). , 1962 .

[9]  F. Sone,et al.  Filarial infection in vector mosquitos after mass drug administration in Western Samoa. , 1975 .

[10]  Shannon K. McClintock,et al.  Xenomonitoring of Wuchereria bancrofti and Dirofilaria immitis infections in mosquitoes from American Samoa: trapping considerations and a comparison of polymerase chain reaction assays with dissection. , 2009, The American journal of tropical medicine and hygiene.

[11]  R. Speare,et al.  The argument for integrating vector control with multiple drug administration campaigns to ensure elimination of lymphatic filariasis , 2006, Filaria journal.

[12]  E. Michael,et al.  Transmission dynamics of lymphatic filariasis: vector‐specific density dependence in the development of Wuchereria bancrofti infective larvae in mosquitoes , 2006, Medical and veterinary entomology.

[13]  P. Kelly,et al.  Lessons from the Pacific programme to eliminate lymphatic filariasis: a case study of 5 countries , 2009, BMC infectious diseases.

[14]  G. Spears,et al.  Epidemiology of subperiodic bancroftian filariasis in Samoa 8 years after control by mass treatment with diethylcarbamazine. , 1985, Bulletin of the World Health Organization.

[15]  A. Clough,et al.  Exploratory study investigating factors influencing mass drug administration (MDA) compliance for lymphatic filariasis in Samoa , 2010 .

[16]  PacELF.  The PacELF way : towards the elimination of lymphatic filariasis from the Pacific , 2006 .

[17]  Shannon K. McClintock,et al.  First evidence of spatial clustering of lymphatic filariasis in an Aedes polynesiensis endemic area. , 2011, Acta tropica.

[18]  T. Burkot,et al.  Evaluation of Three Traps for Sampling Aedes polynesiensis and Other Mosquito Species in American Samoa1 , 2008, Journal of the American Mosquito Control Association.

[19]  Steven A. Williams,et al.  A real-time PCR-based assay for detection of Wuchereria bancrofti DNA in blood and mosquitoes. , 2006, The American journal of tropical medicine and hygiene.

[20]  G. Spears,et al.  Distribution of vectors, transmission indices and microfilaria rates of subperiodic Wuchereria bancrofti in relation to village ecotypes in Samoa. , 1987, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[21]  S. Ritchie,et al.  A Simple Non-Powered Passive Trap for the Collection of Mosquitoes for Arbovirus Surveillance , 2013, Journal of medical entomology.

[22]  G. Pichon.  Limitation and facilitation in the vectors and other aspects of the dynamics of filarial transmission: the need for vector control against Anopheles-transmitted filariasis. , 2002, Annals of tropical medicine and parasitology.

[23]  F. Sone,et al.  The bionomics of filariasis vectors in Western Samoa , 1974 .

[24]  T. Naseri,et al.  Application of the Filariasis CELISA Antifilarial IgG4 Antibody Assay in Surveillance in Lymphatic Filariasis Elimination Programmes in the South Pacific , 2011, Journal of tropical medicine.

[25]  H. Bossin,et al.  Population Studies of the Filarial Vector Aedes polynesiensis (Diptera: Culicidae) in Two Island Settings of French Polynesia , 2013, Journal of medical entomology.

[26]  W. Takken,et al.  Sugar-fermenting yeast as an organic source of carbon dioxide to attract the malaria mosquito Anopheles gambiae s.s. , 2010, Malaria Journal.

[27]  G. Weil,et al.  Detection of Wuchereria bancrofti L3 Larvae in Mosquitoes: A Reverse Transcriptase PCR Assay Evaluating Infection and Infectivity , 2010, PLoS neglected tropical diseases.

[28]  R. Cummings,et al.  Seasonal abundance, diel biting activity and parity of Aedes polynesiensis marks and A. samoanus (Grünberg) (Diptera: Culicidae) in Samoa , 1987 .

[29]  K. Ichimori,et al.  Pacific collaboration to eliminate lymphatic filariasis , 2005, Trends in Parasitology.

[30]  K. Uchida,et al.  Observations on Culex quinquefasciatus Say in relation to transmission of filariasis due to subperiodic Wuchereria bancrofti in Samoa. , 1992, Annals of tropical medicine and parasitology.

[31]  G. Weil,et al.  A Reverse Transcriptase-PCR Assay for Detecting Filarial Infective Larvae in Mosquitoes , 2008, PLoS neglected tropical diseases.

[32]  T R Unnasch,et al.  Determining the prevalence of Onchocerca volvulus infection in vector populations by polymerase chain reaction screening of pools of black flies. , 1995, The Journal of infectious diseases.

[33]  R. Russell.  The relative attractiveness of carbon dioxide and octenol in CDC- and EVS-type light traps for sampling the mosquitoes Aedes aegypti (L.), Aedes polynesiensis Marks, and Culex quinquefasciatus say in Moorea, French Polynesia. , 2004, Journal of vector ecology : journal of the Society for Vector Ecology.

[34]  P. Graves,et al.  Wuchereria bancrofti Filariasis Control in Samoa before PacELF (Pacific Programme to Eliminate Lymphatic Filariasis) , 2007 .

[35]  B. Duke,et al.  Strategies and tools for the control/elimination of lymphatic filariasis. , 1997, Bulletin of the World Health Organization.

[36]  K. Ichimori.  Entomology of the filariasis control programme in Samoa, Aedes polynesiensis and Ae. samoanus , 2001 .

[37]  Steven A. Williams,et al.  Molecular Xenomonitoring Using Mosquitoes to Map Lymphatic Filariasis after Mass Drug Administration in American Samoa , 2014, PLoS neglected tropical diseases.

[38]  R. Cummings,et al.  Natural infections of Wuchereria bancrofti in Aedes (Stegomyia) polynesiensis and Aedes (Finlaya) samoanus in Samoa. , 1987, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[39]  E. Ottesen,et al.  Global Programme to Eliminate Lymphatic Filariasis: The Processes Underlying Programme Success , 2014, PLoS neglected tropical diseases.